By virtue of such advantageous features as light weight, small thickness and low power consumption, liquid crystal display devices have been used in various fields as display devices of OA equipment, such as personal computers, and TVs. In recent years, liquid crystal display devices have also been used as display devices of portable terminal equipment such as mobile phones, car navigation apparatuses, game machines, etc.
In recent years, liquid crystal display panels of a fringe field switching (FFS) mode and in-plane switching (IPS) mode have been put to practical use. The liquid crystal display panel of the FFS mode or IPS mode is configured such that a liquid crystal layer is held between an array substrate, which includes a pixel electrode and a common electrode, and a counter-substrate. The pixel electrode is electrically connected to, for example, a pad electrode via a contact hole formed in an insulation film.
When a lower-layer electrode and an upper-layer electrode, as described above, are electrically connected, there may be a case in which impurities adhere to, or an oxide film forms on, the surface of the lower-layer electrode, as an exposure time of the lower-layer electrode becomes longer during a period from formation of a contact hole, which exposes the lower-layer electrode, to formation of the upper-layer electrode. Consequently, a resistive layer lies between the lower-layer electrode and the upper-layer electrode.
Compared to a gate driver or a source driver, a system driver which controls logic outputs needs to be supplied with a large current, and a variance in resistance needs to be suppressed when the system driver is mounted. If the above-described structure is applied to pads at a time of mounting the system driver, the variance in resistance increases between the pads due to the presence of the resistive layer, and there is concern that malfunction of the system driver occurs or a display defect occurs due to a difference between wiring resistances.